At present, the 3rd Generation Partnership Project (3GPP) protocol describes only a policy of selecting an initial codec rate of each interface for Adaptive Multi-Rate codec (AMR)/Adaptive Multi-Rate Wideband codec (AMR-WB).
For example, a policy of selecting an initial codec rate of an A interface for AMR/AMR-WB is as follows: a low codec rate is selected preferentially to obtain the current channel quality. If the channel quality is confirmed to be good, the codec rate is gradually increased to improve the voice service quality. A policy of selecting an initial codec rate of an Iu interface or an Nb interface for AMR/AMR-WB is as follows: a high codec rate is selected preferentially.
In the scenario of Transcoder Free Operation (TrFO) communication, because selection of the initial codec rate of each interface for AMR/ARM-WB exists collision, for example, if the channel quality is poor, using a high codec rate by the downstream increases the probability of packet loss and packet error, which greatly affects the voice service quality; in addition, the process of initiating a request for reducing a codec rate after poor voice service quality is detected is slow, resulting in non-timely codec rate adjustment.